Minister of Religion

I have had two conflicting opinions from HMRC staff regarding what expenses can be claimed from a Minister of Religion who owns his own house, but uses it as a church office for approximately 52 hours a week including having church members round evenings. Has anyone else had to prepare expenses to get tax relief on for a Minister of Religion? There is a HMRC Helpsheet 236 but it says up to 25% of lighting heating and so on. The "so on" is not very helpful. Wondering whether mortgage interest and council tax are included and what percentage, bearing in mind he will only be paid back 20%